In vitro studies indicate that most cell types, whether derived from embryonic or adult tissue, produce and respond to transforming growth factor-beta (TGF-beta) under cell culture conditions. Virtually all cells possess receptors for this peptide; yet little is known regarding either the identity of cells responsible for TGF-beta synthesis in vivo or the peptides' cellular targets and physiological roles. To address these issues we have raised polyclonal antibodies in rabbits to synthetic peptides corresponding to regions of mature TGF-beta and its precursor. Antibodies have been characterized by their abilities to recognize TGF-beta in radioimmunoassays, enzyme-linked immunoabsorbent assays, Western blots and immunohistochemical systems. Two antibodies which are particularly useful for immunohistochemical localization of TGF-beta, recognize different epitopes of the protein and give different localizations; one antibody gives primarily intracellular staining and seems to recognize TGF-beta at sites of synthesis, while the other antibody gives extracellular staining and may recognize TGF-beta at sites of action or storage. Initial immunohistochemical studies on the role of TGF-beta in the development of the mouse have shown it to be associated with mesenchyme and localized in areas of active morphogenesis. By use of additional peptide antibodies we are expanding these studies to investigate the role of TGF-beta in development of the chick. In addition, we have used these antibodies to localized TGF-beta in neonatal and adult mouse and have seen staining in chondrocytes, renal distal tubules, placental chorion cells, adrenal cortex, cardiac monocytes and bone marrow. Studies in the normal mouse are being used as a baseline for comparitive studies of pathological conditions such as heart ischemia.